the stage and the lights should be crowded into them as closely as
possible. The lighting should be divided into three groups suitable for
three colors. It is customary to have about half of the lights white and
the remaining half divided into two equal parts for different colors. A
small part of the white lights should be arranged upon a separate
circuit so that they may be used for rehearsals or other purposes, when
not very much light is needed.
No very definite recommendations concerning the type of lamp to be used
can be given. In some theaters the stage is very solid and tungsten
lamps are used to advantage; in others the jarring prevents their use.
The white lights should be arranged so that their light need not pass
through the colored lamps. In vaudeville houses some protection in the
form of chains or guards is often provided to prevent objects from being
rolled or thrown against the lights. Figures 161 and 162 show types of
footlights and the manner of installing the sockets.
_The National Electrical Code Rules for Wiring Footlights._
Must be wired in approved conduit or armored cable, each lamp receptacle
being enclosed within an approved outlet box, or the lamp receptacles
may be mounted in an iron or steel box, metal to be of a thickness not
less than No. 20 U. S. sheet metal gauge treated to prevent oxidation
and so constructed as to enclose all the wires. Wires to be soldered to
lugs of receptacles. Must be so wired that no set of lamps requiring
more than 1,320 watts nor more than 26 receptacles shall be dependent
upon one cut-out.
_Fuses._--See “Cut-outs.”
_Gallery Lighting._--The proper lighting of galleries is a difficult
matter where there is another gallery above. In such a case the ceiling
is always very low. An even distribution of light requires the use of
many small incandescent lamps evenly distributed. This will make the
wiring expensive. The light should be taken pretty well from the rear so
as to avoid placing lights in the range of visions of the audience.
Emergency lights should be provided here as well as in the main
auditorium.
_Gallery Pockets._--Pockets for arc lamps are often provided, as it
often happens that a moving-picture machine must be placed in the
gallery. The stage pockets should be wired with number 6 B. & S. gauge
wire, this being the smallest wire allowed to feed a moving-picture arc.
The stage pocket should be controlled by a switch on the switchboard. It
often happens that the operator at the lamp has a wrong cue and his
light can then be controlled by the stage manager at the stage
switchboard.
_Gas Lighting._--Electric gas lighting is very little used at the
present time, but in many theaters the emergency lighting is by gas and,
in order to save the time necessary to light these by hand before every
performance, an automatic gas lighting system has been installed in some
theaters. A diagram of such a system is shown in Figure 163. A battery
of considerable capacity is necessary and also a spark coil _S_. At each
gas jet a magnet _M_ is installed which, when energized, is capable of
turning the gas on and at the same time producing a spark. This magnet
is also capable of turning the gas off. Two buttons are provided, one to
turn the gas on and the other to turn it off.
[Illustration: FIGURE 163.]
As the wiring is always used in connection with gas piping, grounds are
of frequent occurrence, and in order to indicate a ground as soon as it
comes on, the bell and battery shown are provided. If a ground causes a
continuous current, the spark coil will attract the armature, thus
causing the bell to ring continuously.
_National Electrical Code Rule for Gas Lighting._
Electric gas lighting, unless it is the frictional system, must not be
used on the same fixtures with the electric light.
_Grid Floor._--This is the term given to the framework which supports
the pulleys over which the cables for handling curtains and scenery run.
It is usually made up of parallel iron slats or bars; hence the name. A
fairly good illumination should be provided here and all of the lights
should be arranged on three-way switches. One light for every 400 square
feet will be sufficient.
_National Electrical Code Rule for Ground Clamps._
Connections to grounded pipes and to conduit must be exposed to view or
be readily accessible, and must be made by means of approved ground
clamps to which the ground wire must be soldered.
_National Electrical Code Rule for Grounding._
The metal of conduit, armored cable, or metal molding must be
permanently and effectually grounded to water piping, gas piping, or
other suitable grounds, provided that, when connections are made to gas
piping, they must be on the street side of the meter. If the conduit
system consists of several separate sections, the sections must be
bonded to each other, and the system grounded; or each section may be
separately grounded, as required above.
Conduits and gas pipes must be securely fastened in outlet boxes,
junction boxes, and cabinets, so as to secure good electrical
connections.
If conduit, couplings, outlet boxes, junction boxes, cabinets, or
fittings, having protective coating of non-conducting material such as
enamel, are used, such coating must be thoroughly removed from threads
of both couplings and conduit and such surfaces of boxes, cabinets and
fittings where the conduit or ground clamp is secured in order to obtain
the requisite good connection. Grounded pipes must be cleaned of rust,
scale, etc., at place of attachment of ground clamp.
Connections to grounded pipes and to conduit must be exposed to view or
readily accessible, and must be made by means of approved ground clamps
to which the ground wires must be soldered.
Ground wires must be of copper, at least No. 10 B. & S. gauge (where
largest wire contained in conduit is not greater than No. 0 B. & S.
gauge), and need not be greater than No. 4 B. & S. gauge (where largest
wire contained in conduit is greater than No. 0 B. & S. gauge). They
shall be protected from mechanical injury.
The ground on the conduit system is not to be considered as a ground for
a secondary system.
_Guards._--A guard rail should be provided around the stage switchboard
to prevent actors from coming in contact with any live part of the
switchboard. All incandescent lamps about the stage, dressing rooms,
fly-floor, grid-floor, etc., should be provided with guards.
_Hanger-Boards._--Hanger-boards are not compulsory but where not used,
arc lamps must be hung from insulating supports other than their
conductors.
_National Electrical Code Rule for Hanger-Boards for Series Arc Lamps._
Hanger-boards must be so constructed that all wires and current-carrying
devices thereon will be exposed to view and thoroughly insulated by
being mounted on a non-combustible, non-absorptive, insulating
substance. All switches attached to the same must be so constructed that
they shall be automatic in their action, cutting off both poles to the
lamps, not stopping between points when started, and preventing an arc
between points under all circumstances.
_Heaters._--Heaters are used sometimes in cold dressing rooms, in box
offices and in other small spaces where other adequate heating
arrangements have not been made. The fire hazard incident to the use of
electric heaters is considerable and they should be carefully installed
according to the rules given below.
From one-half to three watts per cubic foot will be required to heat a
room. The quantity of heat necessary to be supplied depends largely upon
the ventilation. It will be small in closed dressing rooms and large,
for instance, in the box office. Always place a heater where the air
enters a room; never where it leaves.
_National Electrical Code Rules for Electric Heaters._
Each heater of more than 6 amperes or 660 watts capacity must be
protected by a cut-out, and controlled by a switch or plug connector
plainly indicating whether “on” or “off” and located within sight of
the heater. Heaters of 6 amperes or 660 watts capacity, or less, may be
grouped under the protection of a single set of fuses, provided the
rated capacity of the fuses does not exceed 10 amperes; or may be
connected individually to lighting circuits.
Flexible conductors for smoothing irons and sad irons, and for all
devices requiring over 250 watts, must have an approved insulation and
covering.
With portable heating devices, approved plug connectors must be used so
arranged that the plug may be pulled out to open the circuit without
leaving any live parts so exposed as to render likely accidental contact
therewith. The connector may be located at either end of the flexible
conductor or inserted in the conductor itself.
Smoothing irons, sad irons, and other heating devices that are intended
to be applied to combustible articles, must be provided with approved
stands.
Stationary heaters such as radiators, ranges, plate warmers, etc., must
be so located as to furnish ample protection between the device and
surrounding combustible material.
Must each be provided with a name-plate, giving the maker’s name and the
normal capacity in volts and amperes.
_High Potential._--The National Electrical Code classifies all voltages
below 550 as low. Nevertheless voltages above 220 should not be
considered in the auditorium, stage, or dressing rooms of any theater.
And this voltage only in connection with a three-wire system where the
high voltage exists only between the outside wires, and 110 volts are
used for lamps and other devices. High potential systems should be used
only on the outside.
_Illumination._--Illumination is more an art than a science and the
rules that can be given have only a very general application. The best
practice, where really good illumination is desired, is to install a
large number of circuits in proportion to the number of lights, so that
lamps of large candle power may be used wherever desirable. The quantity
of light needed in theaters varies greatly with the color of decorations
and with their condition. Dust accumulates rapidly in theaters and may
absorb half of the light. If there is plenty of capacity the candle
power of lamps may be changed to suit conditions and obtain any result
desired.
The number of sockets installed in the auditorium varies widely. In some
of the cheaper theaters one light for each twenty seats is considered
sufficient; while in elaborately lighted houses, there are cases where
the number of sockets is equal to about half the number of seats. Good
illumination requires that the light come from the back, but very often
the purpose is to obtain a brilliant effect by placing lights in front
of the audience. In such cases, however, the lamps are always of low
candle power and should be frosted.
_Incandescent Lamps._--Practically all incandescent lamps are now rated
in watts. They can be obtained in voltages ranging from 2 to 250 and may
be operated in series or in multiple. All but the tantalum lamp operates
equally well on alternating or direct current. The tantalum cannot be
recommended for alternating-current circuits. No incandescent lamps will
operate well on frequencies lower than forty cycles. The natural
distribution of light is mostly in the horizontal plane and for good
illumination reflectors should be provided.
The color value is in the following order: Tungsten, tantalum,
graphitized filament, carbon filament. None are equal for color-matching
purposes to the intensified arc or the Moore tube.
The life of all incandescent lamps varies inversely with the voltage. An
increase in voltage will produce an increase in the efficiency of the
lamp but shorten its life. The efficiency decreases with continued use,
and it is generally considered that the useful life of a lamp is over
when its efficiency has fallen to 80 per cent of its original value.
Frosting or coloring shortens the life of lamps from 30 to 50 per cent
and reduces the candle power from 3 to 10 per cent, but the lamp yields
a more pleasing light. Frosting is ordinarily used only where lamps are
placed so as to come in the line of vision. Bowl frosting does not
materially reduce the life of a lamp.
_Efficiency of Lamps._
With incandescent lamps the term “efficiency” has a meaning quite
different from that usually given, it being the number of watts per
candle power. The lower the efficiency of an incandescent lamp, the
better it is and the more light it yields per watt consumed.
_Mazda Lamp._
The Mazda lamp has an efficiency of about 1.25 and is the most efficient
of all. It may be recommended in all places where lamps may be suspended
vertically; where there is not too much jarring; where there is ordinary
care in handling; and where the lamps are burning a large part of the
time. The operating expense of this lamp is low, but the initial cost is
high and the breakage is likely to be considerable. If lamps are much
handled and not burned much, the cost of broken lamps may exceed the
saving in energy. It is best not to clean Mazda lamps when cold. Shock
absorbers should be used where there is much jarring. The illumination
should be laid out for the use of lamps not smaller than 60 watts. The
lamps should not be used for temporary work or for coloring. Arrange
lamps as far as possible to be controlled by switches. Broken filaments
can often be united again by shaking the lamps gently until the broken
ends come together. The current will then weld them. When a bank of
Mazda lamps is turned on there is an excessive current for an instant.
_Tantalum Lamp._
The efficiency of this lamp is from 1.8 to 2 watts per candle power.
This lamp is much used for street-car and similar illumination
because it stands jarring very well. It should not be used on
alternating-current circuits. The filament can often be united in the
same manner as the Mazda.
_Graphitized Filament Lamp._
This lamp has an efficiency of 2.5 watts per candle power.
_Carbon Filament Lamp._
This lamp used on 110-volt circuits has an efficiency of from 3 to 3.2
watts per candle power. The efficiency of the smaller sizes is from 4 to
5 watts per candle power. The carbon filament lamp is the most
expensive of all to operate, but on account of the strength and
cheapness of the lamp it can be recommended in places where the breakage
is liable to be great or where the light is used for comparatively brief
periods.
_National Electrical Code Rules for Incandescent Lamps._
Must be provided with guards when liable to come in contact with
inflammable material or subject to rough usage. Must be protected by
vapor-proof globes where inflammable gases exist.
_National Electrical Code Rules for Insulating Joints._
When supported at outlets in metal conduit, armored cable, or metal
molding systems, or from gas piping or any grounded metal work; or when
installed on metal walls or ceilings, or on plaster walls or ceilings
containing metal lath, or on walls or ceilings in fireproof buildings,
fixtures must be insulated from such supports by approved insulating
joints placed as close as possible to the ceilings or walls. The
insulating joint may be omitted in conduit, armored cable, or metal
molding systems with straight electric fixtures in which the insulation
of conductors is the equivalent to insulation in other parts of the
system, and provided that approved sockets, receptacles, or wireless
clusters are used of a type having porcelain or equivalent insulation
between live metal parts and outer metal shells, if any.
Where insulating joints are required, fixture canopies of metal must be
thoroughly and permanently insulated from metal walls or ceilings, or
from plaster walls or ceilings on metal lathing, and from outlet boxes.
Canopy insulators must be securely fastened in place, so as to separate
the canopies thoroughly and permanently from the surfaces and outlet
boxes from which they are designed to be insulated.
_Inverted Lighting._--In this method of lighting the light is first
thrown upward against the ceiling and then reflected back. This method
can be used to advantage with light colored ceilings only. It is
especially suited for low ceilings and with high ceilings the advantage
disappears. The light obtained in this manner is very even and almost
shadowless. Much light is lost through absorption but, owing to the fact
that the light is of such an even quality, the eye readily accommodates
itself to a lower quantity and the net increase in energy required to
illuminate suitable spaces is not so very great. Those who wish to go
into the subject of illumination thoroughly will find it treated fully
in “Modern Illumination Theory and Practice”.
_Joints._--Methods of making joints are illustrated in Figure 164. Be
careful not to overheat, especially at points where there is a strain on
the wire.
_National Electrical Code Rule for Joints._
Wires must be so spliced or joined as to be both mechanically and
electrically secure without solder. The joints must then be soldered
unless made with some form of approved splicing device, and covered with
an insulation equal to that on the conductors.
[Illustration: FIGURE 164.]
Stranded wires (except in flexible cords) must be soldered before being
fastened under clamps or binding screws; and, whether stranded or solid,
when they have a conductivity greater than that of No. 8 B. & S. gauge
they must be soldered into lugs for all terminal connections, except
where an approved solderless terminal connector is used.
_Junction Boxes._--Junction boxes are installed in conduit systems for
the purpose of facilitating the drawing in of the wire or of branching
off from a main run. See “Conduit Work.”
_Lamps._--See “Incandescent Lamps.”
_Lobby._--The lobby generally requires a number of lights and the aim
often is to create a lavish display. Very often a cut-out center is
arranged at some convenient place. The exit and emergency lights must be
controlled from the lobby. Sometimes outlets are provided for electric
bulletin boards or small signs.
_Lugs._--For solderless lugs, such as are used on rheostats or for arc
lamps, see “Portable Stage Equipment.”
_National Electrical Code Rule for Lugs._
For fuses rated over 30 amperes lugs, firmly screwed or bolted to the
terminals and into which the conducting wires are soldered, must be
used. On rheostats, resistances, etc., lugs will not be required when
leads are provided as a part of the device.
Switches for current of over 30 amperes must be equipped with lugs,
firmly screwed or bolted to the switch, and into which the conducting
wires shall be soldered. For the smaller sized switches simple clamps
can be employed, provided they are heavy enough to stand considerable
hard usage.
Where lugs are not provided, a rugged double-V groove clamp is advised.
A set screw gives a contact at only one point, is more likely to become
loosened, and is almost sure to cut into the wire. For the smaller
sizes, a screw and washer connection with up-turned lugs on the switch
terminal gives a satisfactory contact.
_National Electrical Code Rules for Metal Moldings._
Must not be used on stage side of proscenium wall.
Must not be used for circuits carrying more than 1,320 watts.
Wire used must be standard rubber covered, but may be single braid.
Must never be concealed or run in damp places.
Must not be used where the difference of potential exceeds 300 volts.
Must be continuous from outlet to outlet, to junction boxes, or approved
fittings designed especially for use with metal moldings, and must at
all outlets be provided with approved terminal fittings which will
protect the insulation of conductors from abrasion, unless such
protection is afforded by the construction of the boxes or fittings.
Such molding where passing through a floor must be carried through an
iron pipe extending from the ceiling below to a point five feet above
the floor, which will serve as an additional mechanical protection and
exclude the presence of moisture often prevalent in such locations.
Where the mechanical strength of the molding itself is adequate, this
ruling may be modified to require the protecting piping from the ceiling
below to a point at least three inches above the flooring.
Where such moldings pass through a partition the iron pipe, required for
passing through floors, may be omitted and the molding passed directly
through, providing the partition is dry and the molding is in a
continuous length with no joint or coupling within the partition.
Backing must be secured in position by screws or bolts, the heads of
which must be flush with the metal.
Must have the metal of molding permanently and effectually grounded to
water piping, gas piping, or other suitable grounds, provided that when
connections are made to gas piping, they must be on the street side of
the meter. If the metal molding system consists of several separate
sections, the sections must be bonded to each other and the system
grounded, or each section may be separately grounded, as required above.
Metal moldings and gas pipes must be securely fastened to outlet boxes,
junction boxes, and cabinets, so as to secure a good electrical
connection. Molding must be so installed that adjacent lengths of
molding will be mechanically and electrically secured at all points.
If metal molding, couplings, outlet boxes, junction boxes, cabinets, or
fittings having protective coating of non-conducting material such as
enamel are used, such coating must be thoroughly removed from threads of
couplings and metal moldings, and from the surfaces of boxes, cabinets,
and fittings, where the metal molding or ground clamp is secured in
order to obtain the requisite good connection. Grounded pipes must be
cleaned of rust, scale, etc., at the place of attachment of the ground
clamp.
Connection to grounded pipes and to metal moldings must be exposed to
view, or readily accessible, and must be made by means of approved
ground clamps, to which the wires must be soldered.
Ground wires must be of copper, at least No. 10 B. & S. gauge. They
shall be protected from mechanical injury.
[Illustration: FIGURE 165.]
Must be installed so that for alternating-current systems the two or
more wires of a circuit will be in the same metal molding. It is
suggested that this be done for direct-current systems also so that they
may be changed to the alternating-current system at any time, induction
troubles preventing such change if the wires are in separate moldings.
_Meters._--A good job of meter setting requires that the meter fittings
which are now on the market be used. Two separate meters will be
required in each theater; one for the general lighting and one for the
emergency system.
_Meter Reading._--Meter readings are indicated by pointers, arranged to
move over dials as shown in Figure 165. The various pointers are
connected together by gearing in such a manner, that alternate pointers
move in opposite directions, as indicated by the figures on the dials.
The gearing moving the pointers in Figure 165 is of such proportions
that a total revolution of any pointer represents one-tenth of a
revolution of the pointer to the left of it. Thus ten revolutions of one
pointer causes one revolution of the one at the left.
[Illustration: FIGURE 166.]
[Illustration: FIGURE 167.]
At the top of each dial the value of the reading of that dial is shown.
Where the figures given are followed by the letter “s”, as in Figures
167 and 168, it signifies that each division of the dial represents the
amount of energy indicated by the figures at the top. For instance, in
Figure 168 each division of the dial at the right represents one-tenth
of one kilowatt hour and a total revolution of the pointer ten-tenths,
or one kilowatt hour.
If the figures given at the top of the dial are not followed by the
letter “s”, or as shown in Figure 166, each division of the dial
represents one-tenth of the amount shown at the top of the dial, the
dial at the right of Figure 166 indicating nine-tenths of ten kilowatts
or nine kilowatts.
[Illustration: FIGURE 168.]
The meter must always be read from right to left, the lowest indicating
dial being the one at the extreme right, and the lower reading ones
always being used to check the higher ones just at the left. The
following example will illustrate the manner of reading meters:
In Figure 165 the right-hand pointer registers nine-tenths of 1000, or
900 watt hours; the pointer next to it registers eight, since it cannot
be considered as fully up to any number unless the pointer at the right
of it has just arrived at or passed 0. By the same token the middle
pointer also registers 8 and as the middle pointer has not reached 0 the
one at the left of it must be read as one, the last dial also indicates
one and the total reading is 1,188,900. On some types of meters a
multiplier is used. This is generally given on the meter dial and the
readings given by the pointers must be multiplied by this number to
obtain the correct reading of the meter.
_Motors._--Motors are used in theaters for ventilation, for raising and
lowering the steel curtain in cities where such are required, and also
in some cases for operating drop curtains, but for this last purpose
they have not found much favor. In some localities motors are required
to keep up a certain water pressure to be used in case of fire. Voltages
higher than 550 are not considered in theater work.
_National Electrical Code Rules for 550-volt Motors and Less._
Motors operating at a potential of 550 volts or less must be thoroughly
insulated from the ground wherever feasible. Wooden base frames used for
this purpose, and wooden floors, which are depended upon for insulation
where, for any reason, it is necessary to omit the base frames, must be
kept filled to prevent absorption of moisture, and must be kept clean
and dry. Where frame insulation is impracticable special permission in
writing may be given for its omission, in which case the frame must be
permanently and effectively grounded.
The motor leads or branch circuits must be designed to carry a current
at least 25 per cent greater than that for which the motor is rated.
Where the wires under this rule would be over-fused in order to provide
for the starting current, as in the case of many of the
alternating-current motors, the wires must be of such size as to be
properly protected by these larger fuses.
Each motor and resistance box must be protected by a cut-out and
controlled by a switch; said switch plainly indicating whether “on” or
“off”.
Small motors may be grouped under the protection of a single set of
fuses, provided the rated capacity of the fuses does not exceed 6
amperes. With motors of one-fourth horse power or less, on circuits
where the voltage does not exceed 300, single-pole switches may be used.
The switch and rheostat must be located within sight of the motor,
except in cases where special permission to locate them elsewhere is
given, in writing.
Where the circuit-breaking device on the motor-starting rheostat
disconnects all wires of the circuit, the switch called for in this
section may be omitted. Overload-release devices on motor-starting
rheostats will not be considered to take the place of the cut-out
required by this section. An automatic circuit-breaker disconnecting all
wires of the circuit may serve as both switch and cut-out.
Auto starters, unless equipped with tight casings enclosing all
current-carrying parts, in all wet, dusty, or linty places, must be
enclosed in dust-tight, fireproof cabinets. Where there is any liability
of short circuits across their exposed live parts being caused by
accidental contacts, a railing must be erected around them.
Must not be run in series-multiple or multiple-series, except on
constant-potential systems, and then only by special permission.
Must, when combined with ceiling fans, be hung from insulated hooks, or
else there must be an insulator interposed between the motor and its
support.
Must each be provided with a name-plate, giving the maker’s name, the
capacity in volts and amperes, and the normal speed in revolutions per
minute.
All varying (or variable) speed alternating-current motors except those
used for railway service must be marked with the maximum current which
they can safely carry for 30 minutes, starting cold.
Terminal blocks when used on motors must be made of approved
non-combustible, non-absorptive, insulating material such as slate,
marble, or porcelain.
Adjustable-speed motors, unless of special and appropriate design, if
controlled by means of field regulation, must be so arranged and
connected that they cannot be started under weakened field.
The use of soft rubber bushings to protect the lead wires coming through
the frames of motors is permitted, except when installed where oils,
grease, oily vapors, or other substances known to have rapid deleterious
effect on rubber are present in such quantities and in such proximity to
motors as may cause such bushings to be liable to rapid destruction. In
such cases hardwood properly filled, or preferably porcelain or micanite
bushings must be used.
The following table shows the sizes of wire recommended to be used with
motors of the horsepower given. This table is an extract from the rules
of the Department of Gas and Electricity of the City of Chicago. The
column headed “Mains” may be used when there are a number of motors fed
by a single line. For all lines which supply a single motor only, the
column headed “Branches” must be used.
The difference between the two is due to the fact that it is not
believed that several motors fed by a single line will all be started at
the same time; hence it is not necessary to provide the overload
capacity for all of the motors as it is where but a single motor is
installed.
TABLE VIII.
SIZE OF WIRES FOR MOTORS OF DIFFERENT HORSE POWER.
DIRECT CURRENT
------------------------------------+------------------------------
110 Volts | 220 Volts
-----+---------+---------+----------+---------+---------+----------
H. P.| Full- | Size of | Size of | Full- | Size of | Size of
| load | Wire | Wire | load | Wire | Wire
| Current | Mains | Branches | Current | Mains | Branches
-----+---------+---------+----------+---------+---------+----------
1 | 8 | 14 | 14 | 4 | 14 | 14
2 | 15 | 14 | 12 | 8 | 14 | 14
3 | 23 | 10 | 8 | 12 | 14 | 14
4 | 30 | 8 | 6 | 15 | 14 | 12
5 | 38 | 6 | 6 | 19 | 12 | 10
7.5 | 56 | 5 | 4 | 28 | 8 | 8
10 | 75 | 3 | 1 | 38 | 6 | 6
-----+---------+---------+----------+---------+---------+----------
SINGLE-PHASE
-----+---------+---------+----------+---------+---------+----------
1 | 12 | ... | 12 | 6 | ... | 14
2 | 23 | ... | 8 | 11 | ... | 12
3 | 33 | ... | 6 | 16 | ... | 10
4 | 44 | ... | 4 | 22 | ... | 8
5 | 53 | ... | 3 | 26 | ... | 6
-----+---------+---------+----------+---------+---------+----------
THREE-PHASE
-----+---------+---------+----------+---------+---------+----------
1 | ... | ... | ... | 3 | 14 | 14
2 | ... | ... | ... | 5 | 14 | 14
3 | ... | ... | ... | 8 | 14 | 14
4 | ... | ... | ... | 10 | 14 | 14
5 | ... | ... | ... | 13 | 14 | 12
7.5 | ... | ... | ... | 19 | 12 | 8
10 | ... | ... | ... | 26 | 8 | 6
-----+---------+---------+----------+---------+---------+----------
_Music Stands._--Music stands are used by the musicians and are
generally placed between the first row of seats and the stage. Each
musician should be provided with an individual stand, although if
necessary, two or three can get along with one stand.
No first-class theater should be fitted up with less than twenty outlets
for musicians’ lights. In the Metropolitan Opera House of New York there
are one hundred. Houses used exclusively for vaudeville do not, however,
need that many. In houses devoted to grand opera, often as many as one
hundred or more musicians are employed at the same time. To take care of
such a number, the music stands should be wired with pin-plug connectors
so that connections may be made from one to the other. Long flexible
connections are necessary for most music stands.
Sometimes it is necessary to crowd the orchestra under the stage and at
other times, with musical comedies, for instance, they must be brought
out where they can see the movements of the actors.
The more the circuits are subdivided, and the different lights made
independent of each other, the better it will be and the less the
annoyance in case a fuse blows. The fuses should always be arranged at
the switchboard so that it will not be necessary for the electrician to
work in front of the audience in cases of trouble. For this reason extra
stands should also be kept on hand.
A main switch controlling the lights should be placed where one of the
musicians can handle it. In dark scenes these lights must often be
turned out. If these lights are left under the control of the stage
electrician they will be more likely to be forgotten at the critical
moment than if under the control of the men who need them.
An eight candle-power lamp for each stand will be sufficient and this is
usually placed inside a special reflector which allows the light to fall
upon the music sheet only. Stage cable of good quality should be used
for the connections; there is too much rough handling for reinforced
cord. The use of the ordinary attachment plug should be avoided; use
approved pin-plug connectors.
_Open Work._--Open work is not allowed in theaters.
_Operating Room._--See special chapter on “Operating Room.”
_Panel Boards._--Panel boards are really small switchboards, the
switches and cut-outs being mounted usually upon slate. The slate must
be free of metal seams; these, if present, often manifest themselves by
heating. Panel boards, unless located in the immediate vicinity of the
main switchboard, and where they are enclosed in a compartment, must
always be placed in standard metal cabinets.
_National Electrical Code Rules for Panel Boards._
The following specifications are intended to apply to all panel and
distributing boards used for the control of light and power circuits,
but not to such switchboards in central stations, sub-stations, or
isolated plants as directly control energy derived from generators or
transforming devices.
_Design._
The specifications for construction of switches and cut-outs given in
the following pages must be followed as far as they apply.
In the relative arrangement of fuses and switches, the fuses may be
placed between the bus-bars and the switches, or between the switches
and the circuits, except in the case of service switches. When the
branch switches are between the fuses and the bus-bars, the connections
must be so arranged that the blades will be dead when the switches are
open.
When there are exposed live-metal parts on the back of a board, a space
of at least one-half inch must be provided between such live metal parts
and the cabinet in which the board is mounted.
_Spacings._
TABLE IX.
THE MINIMUM DISTANCE THAT MUST BE MAINTAINED BETWEEN BARE LIVE METAL
PARTS (BUS-BARS, ETC.)
-------------------+---------------------------+--------------
| Between Parts of Opposite |
| Polarity, Except |
| at Switches and | Between
| Link Fuses | Parts of
+------------+--------------+ Same Polarity
| When | | at Link
| Mounted on | When Held | Fuses
| the Same | Free in Air |
| Surface | |
+------------+--------------+--------------
Not over 125 volts | 3/4 inch | 1/2 inch | 1/2 inch
Not over 250 volts | 1-1/4 inch | 3/4 inch | 3/4 inch
Not over 600 volts | 2 inch | 1-3/4 inch |
-------------------+------------+--------------+--------------
At switches or enclosed fuses, parts of the same polarity may be placed
as close together as convenience in handling will allow. It should be
noted that the above distances are the minimum allowable, and it is
urged that greater distances be adopted wherever the conditions will
permit.
The spacings given in the first column apply to the branch conductors
where enclosed fuses are used. Where link fuses or knife switches are
used, the spacings must be at least as great as those given in the
following section on fuse spacing. The spacings given in the second
column above apply to the distance between the raised main bars and
between these bars and the branch bars over which they pass. The
spacings given in the third column are intended to prevent the melting
of a link fuse by the blowing of an adjacent fuse of the same polarity.
Panel boards of special design, in which the insulation and separation
between the bus-bars, and between the other current-carrying parts is
secured by means of barriers or insulating materials instead of by the
spacings given above, must be submitted for special examination and
approved before being used.
_Fuse Spacings._
Spacings must be at least as great as those given in Table X, which
applies only to plain, open link fuses. The spaces given are correct for
fuse blocks to be used on direct-current systems, and can therefore be
safely followed in devices designed for alternating currents. If the
copper fuse tips overhang the edges of the fuse block terminals, the
spacings should be measured between the nearest edges of the tips.
A space must be maintained between fuse terminals of the same polarity
of at least one-half of an inch for voltages up to 125 and of at least
three-quarters of an inch for voltages from 125 to 250. This is the
minimum distance allowable, and greater separation should be provided
when practicable.
For 250 volts, boards, or blocks with the ordinary front-connected
terminals, except where these have a mass of compact form equivalent to
the back-connected terminals usually found in switchboard work, a
substantial barrier of insulating material, not less than one-eighth of
an inch in thickness, must be placed in the “break” gap--this barrier to
extend out from the base at least one-eighth of an inch farther than any
bare live part of the fuse-block terminal, including binding screws,
nuts and the like.
For three-wire systems cut-outs must have the break-distance required
for circuits of the potential of the outside wires.
TABLE X.
FUSE SPACINGS.
---------------------+----------------------+-------------
|Minimum Separation of | Minimum
|Nearest Metal Parts of| Break
|Opposite Polarity | Distance
Not over 125 volts: +----------------------+-------------
10 amperes or less | 3/4 inch | 3/4 inch
11-100 amperes | 1 inch | 3/4 inch
101-300 amperes | 1 inch | 1 inch
301-1,000 amperes | 1-1/4 inches | 1-1/4 inches
---------------------+----------------------+-------------
|Minimum Separation of | Minimum
|Nearest Metal Parts of| Break
|Opposite Polarity | Distance
Not over 250 volts: +----------------------+-------------
10 amperes or less | 1-1/2 inches | 1-1/4 inches
11-100 amperes | 1-3/4 inches | 1-1/4 inches
101-300 amperes | 2 inches | 1-1/2 inches
301-1,000 amperes | 2-1/2 inches | 2 inches
---------------------+----------------------+-------------
_Switch Spacings and Dimensions._
When designed with 250-volt spacings between adjacent blades,
triple-pole switches must be marked 250 volts and may be used on 3-wire
D. C. or single-phase systems having not more than 250 volts between
adjacent wires and not more than 500 volts between the two outside
wires.
Spacings and dimensions must be at least as great as those given below:
TABLE XI A.
SWITCH SPACINGS AND DIMENSIONS FOR SWITCH-BOARDS AND PANEL BOARDS.
_Not Over 125 Volts D. C. and A. C._
--------+--------------------------+---------------+-----------
| | Minimum |
| | Separation of |
Current| Width and Thickness | Nearest Metal | Minimum
--------+--------------------------+ parts of | Break
| Blades | Clips and | Opposite | Distance
| | Hinges | Polarity |
--------+-------------+------------+---------------+-----------
30 amp. | 1/2 inch by | 1/2 inch by| 1 inch | 3/4 inch
60 amp. | 5/64 inch | 3/64 inch | 1-1/4 inch | 1-3/4 inch
--------+-------------+------------+---------------+-----------
TABLE XI B.
SWITCH SPACINGS AND DIMENSIONS FOR INDIVIDUAL SWITCHES.
_Not Over 125 Volts D. C. and A. C._
Inch Inch Inch Inch
30 amperes 1/2 by 5/64 1/2 by 3/64 1-1/4 1
60 and 100 amperes 1-1/2 1-1/4
200 amperes 2-1/4 2
400 and 600 amperes 2-3/4 2-1/2
800 and 1000 amperes 3 2-3/4
A 300-ampere switch with the spacings of the 200-ampere switch above may
be used on switchboards.
TABLE XI C.
SWITCH SPACINGS AND DIMENSIONS FOR ALL SWITCHES.
_250 Volts Only D. C. and A. C._
Inch Inch Inch Inch
30 amperes 1/2 by 5/64 1/2 by 3/64 1-3/4 1-1/2
TABLE XI D.
SWITCH SPACINGS AND DIMENSIONS FOR ALL SWITCHES.
_Not Over 250 Volts D. C. nor Over 500 Volts A. C._
Inch Inch Inch Inch
30 amperes 5/8 by 1/8 5/8 by 1/16 2-1/4 2
60 and 100 amperes 2-1/4 2
200 amperes 2-1/2 2-1/4
400 and 600 amperes 2-3/4 2-1/2
800 and 1000 amperes 3 2-3/4
A 300-ampere switch with the spacings of the 200-ampere switch above may
be used on switchboards.
Cut-out terminals on switches for over 250 volts must be designed and
spaced for 600-volt fuses.
TABLE XI E.
SWITCH SPACINGS AND DIMENSIONS FOR ALL SWITCHES.
_Not Over 600 Volts D. C. and A. C._
Inch Inch Inch Inch
30 amperes 5/8 by 1/8 5/8 by 1/16 4 3-1/2
60 amperes 4 3-1/2
100 amperes 4-1/2 4
_Paint Bridge._--The paint bridge is usually a scaffold which can be
raised and lowered, and which serves the purpose of carrying scene
painters at work on the curtains. A long strip is the best means of
illumination and it must be connected with long stage cable so as to be
portable.
_Paint Room._--Rooms in which paints are stored should not contain
switches or cut-outs. Lamps should be incased in vapor-tight globes.
_Program Board._--A simple form of program board is shown in Figure 169.
Except at the top and the bottom, where three lamps are shown together
in one compartment, each lamp is incased by itself. In front of the
lamps is usually colored glass, bearing numbers or letters. The lamp
behind any number being turned on, that number becomes visible. The top
and bottom are usually labeled, “Special”, or “Extra”.
[Illustration: FIGURE 169.]
Another form of program board is shown in Figure 170. This requires much
more wiring. Each lamp on the board is connected to a plug or switch at
the operator’s station. Whichever switch is closed on the small board at
the right causes a corresponding light on the large board to appear.
[Illustration: FIGURE 170.]
Two program boards are usually installed, one at each side of the stage,
facing the audience at angles, so that one can be seen from the extreme
right, the other from the extreme left.
[Illustration: FIGURE 171.]
A system that is often used for carriage call is shown in Figure 171.
The lights are arranged on circuits as indicated by numbers. All lamps
bearing the same number being connected to one wire leading to the
controlling station. Thus there are eight controlling or switch wires
and there is one wire common to all. A special switch is provided which
has a contact point for each wire. Paper cards, perforated specially for
the numbers they represent, are used. If a card bearing a certain number
is inserted in the proper place and the switch closed, the number
printed on the card will appear on the sign. If, for instance, the
shaded circles in the card at the left of the figure allow contact to be
made, the lights indicated by black circles will light up and make the
figure “6”.
Another form of program or call board is shown in Figure 172. This
requires more wires than the one just described, one wire being carried
to the controlling board from each lamp. The connections may be made in
various ways. Sometimes they are made with knife switches. If it is
desired to make the figure 1, for instance, only the three lights in a
vertical row in the center need be lighted, and to do this the three
wires from those lamps must be connected to one switch. To make the
figure 2, seven lamps would have to be lit by another switch. It is
capable of making any letter or number and when used as a program board
only may be somewhat simplified.
[Illustration: FIGURE 172.]
In connection with these signs a large number of wires may be required
and attention should be given to the following rule:
_National Electrical Code Rule for Wiring Program and Call Boards._
Except in the case of stage pockets the same conduit must never contain
more than four two-wire, or three three-wire circuits of the same system
except by special permission, and must never contain circuits of
different systems.
_Proscenium Side Lights._--These lights are located on each side of the
stage, as near as possible to the edge of the proscenium opening and
often in front of the steel curtain. They are of more use in musical
productions, where choruses spread over the whole stage, than in
dramatic productions where the interest is more in the center of the
stage. In some theaters the proscenium side lights extend the full
height of the opening and are arranged for three colors in the same
manner as footlights and borders. Very often, however, only ten or
twelve lights are arranged on each side of the stage.
The construction rules are the same as those governing foot-lights.
Lamps must be protected by strong wire mesh. This is essential as in
many cases actors are very likely to back into them while passing off
the stage. Portable strips are sometimes used as proscenium side lights.
_Receptacles._--See “Stage Pockets”.
_Retiring Rooms._--In these places a quiet subdued illumination is
usually desired. There are also often quaint objects and effects to be
illuminated. A large number of outlets conveniently located for the use
of table lamps, fire places, and illumination of pictures, should be
provided.
_Rheostats._
_National Electrical Code Rules for Rheostats._
_Location._
Must be placed on a switchboard, or at a distance of at least one foot
from combustible material, or separated therefrom by a slab or panel of
non-combustible, non-absorptive, insulating material such as slate,
soapstone, or marble, somewhat larger than the rheostat, which must be
secured in position independently of the rheostat supports. Bolts for
supporting the rheostat shall be countersunk at least one-eighth inch
below the surface at the back of the slab and the bolt heads shall be
covered with insulating material. For proper mechanical strength, slab
should be of a thickness consistent with the size and weight of the
rheostat, and in no case to be less than one-half inch.
If resistance devices are installed in rooms where dust or combustible
flyings would be liable to accumulate on them, they must be equipped
with dust-proof face plates.
_Materials._
Must be made entirely of non-combustible materials, except such minor
parts as handles, magnet insulation, etc. All segments, lever arms,
etc., must be mounted on non-combustible, non-absorptive, insulating
material.
_Connections._
Clamps for connecting wires to the terminals must be so designed as to
insure a thoroughly good connection and must be sufficiently strong and
heavy to withstand hard usage. For currents above 30 amperes, lugs into
which the connecting wires may be soldered, or approved solderless
connectors must be used. Clamps or lugs will not be required when leads
are provided as a part of the device.
_No-Voltage Release._
Motor-starting rheostats must be so designed that the contact arm cannot
be left on intermediate segments, and for direct-current circuits must
be provided with an automatic device which will interrupt the supply
circuit before the speed of the motor falls to less than one-third of
its normal value. In motor-starting rheostats for alternating-current
circuits the automatic interrupting device may be omitted.
_Overload Release._
Overload-release devices which are inoperative during the process of
starting a motor will not be approved, unless other circuit-breakers or
fuses are installed in connection with them.
_Signals._--Signals are necessary between the manager’s office and the
stage electrician’s station; for this purpose telephones are generally
used. In many cities a fire-alarm signal system is also required and it
is specified to what part of the house it shall lead. In addition to the
above, a means of signalling the fly floor and the orchestra leader must
be provided. Buzzers are used for these signals. It is best to use
batteries for all these signals instead of attempting to run them from
lighting circuits. Means of signalling the arc-lamp station in the
gallery or the balcony should also be provided for use in connection
with lantern slides, etc. Telephone connection to this point will also
be very useful in order to give instructions to the lamp operator.
Return-call systems are advisable in all places so that the electrician
can be called from any point.
In some cities the local laws require these wires to be in conduit so as
to preclude any possibility of their communicating fire to anything. At
any rate the wires should be very carefully installed.
_Signs._--In nearly all electric signs used about theaters the letters
are outlined by incandescent lamps. Small candle-power lamps are always
used. They are not only economical but much more attractive because the
glare from too much light is very annoying. Many signs are equipped with
low candle-power tungsten lamps wired in series. In order that the
letters should show to full advantage they should be glossy white and be
kept clean. Such letters will show as bright as the lamps. It is best to
wire the sign so that either side can be used independent of the other.
In many cases, also, signs are wired so that each letter is independent
of the others for use with flashers.
Attraction signs are used to advertise the attractions which appear from
time to time. Independent portable letters are used and changed as often
as the attractions change. Each letter must be fitted with cable and
attachment plug of some kind and should have a separate circuit.
Cut-outs are generally located on the frame and must be protected from
the weather.
_Sockets._--Sockets must be of approved construction. Key sockets must
not be used for emergency or exit lighting. Sockets with fiber linings
must not be used unless protected by insulating joints. In damp places
weatherproof sockets must be used. Where inflammable gases exist, lamps
must be incased in vapor-proof globes. Porcelain sockets should not be
used in theaters. Weatherproof sockets are generally used for portable
purposes because they have no screws, etc., to work loose.
_Stage Cable._--Stage cables are allowed in theaters only where flexible
conductors are absolutely necessary. All wiring that can possibly be
installed in conduit or strip construction should be so arranged. By the
use of plugging boxes the quantity of stage cable necessary can be much
reduced. Plugs for arc and incandescent lights must not be
interchangeable.
_Stage Flues._--In most cities stage flues, as described in the chapter
on “Theater Buildings”, are required. The requirement is also, often,
that they be released by electrical means. The rule below contemplates a
circuit containing an electro-magnet and at least two switches in
series. The magnet must be energized to hold the ventilator closed. If
the current fails or a switch is opened the dampers must fly open at
once. Where direct current is available the magnet is usually wound for
110 volts and connected to a circuit that is always alive. In case of an
isolated plant which is shut down at night some arrangement for tying
the dampers down should be made, but it is not always advisable, as once
tied they are likely to remain so and sure to fail when needed. Magnets
do not work well on alternating currents and in such cases the magnet
should be wound for a small current to be obtained from a gravity
battery which may be allowed to be always working. Locate the battery
where it will not freeze.
_National Electrical Code Rules for Control of Stage Flues._
In cases where dampers are released by an electric device, the electric
circuit operating same must be normally closed. Magnet operating dampers
must be wound to take full voltage of circuit by which it is supplied,
using no resistance device, and must not heat more than normal for
apparatus of similar construction. It must be located in loft above
scenery, and be installed in a suitable iron box with a tight,
self-closing door.
Such dampers must be controlled by at least two standard single-pole
switches mounted within approved iron boxes provided with self-closing
doors without lock or latch, and located, one at the electrician’s
station and the others as designated.
_Stage and Gallery Pockets._--Stage pockets are usually located on each
side of the stage just far enough from the center to be safely back of
the scenery. The more pockets there are the better it will be. Each
pocket usually contains four circuits, and one of these at least should
be for incandescent lights. It will be convenient if the stage pockets
are divided into four groups, each group under control of a separate
switch and the whole again under control of a main switch. This will
enable the operator to throw off all of the pockets at once, if
necessary, or to make any combination desired.
[Illustration: FIGURE 173.]
Sometimes lights fed through stage pockets require to be dimmed; but it
is hardly practicable to arrange dimmers for apparatus carried by
traveling companies, since a dimmer must be selected with respect to the
amperage it is to control.
In addition to the rules given below, some cities require the bottom of
stage pockets to be open, so as to avoid an accumulation of dust. This
is a very essential precaution, as otherwise the pockets soon fill up or
require very frequent cleaning. The covers must be substantial as heavy
trucks are sometimes run over them. Two illustrations of stage pockets
are given in Figures 173 and 174. The plugs used with these boxes are
shown in Figure 175.
[Illustration: FIGURE 174.]
[Illustration: FIGURE 175.]
Gallery pockets are not usually laid in the floor but along the railing.
The gallery pockets should be under separate control from the stage
switchboard.
_National Electrical Code Rules for Stage and Gallery Pockets._
Must be of approved type, insulated from ground and controlled from
switchboard, each receptacle to be of not less than 35-ampere rating for
arc lamps nor 15-ampere for incandescent lamps, and each receptacle to
be wired to its full capacity. Arc pockets to be wired with wire not
smaller than No. 6 B. & S. gauge and incandescent pockets with not less
than No. 12 B. & S. gauge. Plugs for arcs and incandescent pockets must
not be interchangeable.
_Switches._--All knife switches should be enclosed in cabinets unless
they are located on a switchboard. In exposed places, flush switches
should be used. The usual height at which scattered switches are located
is about four and one-half feet above floor. Door switches are of use
principally in dressing rooms.
[Illustration: FIGURE 176.]
Diagrams of three-way switches are given in Figures 176 and 177. In
Figure 177, the wiring by which a light can be controlled from three
different points is shown. The middle switch must be a pole-changing
switch. In this case a throw-over knife switch is wired to perform this
function. Omitting the knife switch we have two three-way switches
controlling the light. When both switches (indicated by broken lines)
connect to the same wire the light burns.
[Illustration: FIGURE 177.]
In Figure 176, when both switches connect to the same polarity the light
is out; when one of them is connected to the other pole the light burns.
Under certain conditions this arrangement is more economical in wire but
has the disadvantage which the other method avoids, of bringing both
poles to each switch. This method cannot be used with direct-current
arc lamps. Three-way switches are useful on stairways, enabling one to
turn on a light at the bottom of the stairway and turn it off when at
the top or vice versa.
_National Electrical Code Rules for Switches and Connections._
_Switches._
Must be placed on all service wires, either overhead or underground, in
the nearest readily accessible place to the point where the wires enter
the building, and arranged to cut off the entire current. Departure from
this rule may be authorized only under special permission in writing.
Switches controlling emergency lighting must be located only in the
lobby.
Must when used for service switches, indicate, on inspection, whether
the current be “on” or “off”. Switch cabinets must be deep enough to
allow the door to be closed when 30 ampere branch-circuit switches are
in any position, and when larger single-throw switches are thrown open
as far as their construction and installation will permit.
Must, for constant-current systems, close the main circuit and
disconnect the branch wires when turned “off”; must be so constructed
that they shall be automatic in action, not stopping between points when
started, and must prevent an arc between the points under all
circumstances. They must indicate whether the current be “on” or “off”.
Service cut-out and switch must be arranged to cut off current from all
devices including meters.
Must always be placed in dry, accessible places, and be grouped as far
as possible. Single-throw knife switches must be so placed that gravity
will not tend to close them. Double-throw knife switches may be mounted
so that the throw will be either vertical or horizontal as preferred,
but if the throw be vertical a locking device must be provided, so
constructed as to insure the blades remaining in the open position when
so set.
When practicable switches must be so wired that blades will be “dead”
when the switch is open.
When switches are used in rooms where combustible flyings would be
likely to accumulate around them, they must be enclosed in dust-tight
cabinets.
Up to 250 volts and thirty amperes, approved indicating snap switches
are suggested in preference to knife switches on lighting circuits.
Single-pole switches must never be used as service switches nor for the
control of outdoor signs or circuits located in damp places, nor placed
in the neutral wire of a three-wire system, except in the two-wire
branch or tap circuit supplying not more than 660 watts.
Where flush switches or receptacles are used, whether with conduit
systems or not, they must be enclosed in an approved box constructed of
iron or steel, in addition to the porcelain enclosure of the switch or
receptacle.
Hinges of knife switches must not be used to carry current unless they
are equipped with spring washers, held by lock-nuts or pins, or their
equivalent, so arranged that a firm and secure connection will be
maintained at all positions of the switch blades.
Spring washers must be of sufficient strength to take up any wear in the
hinge and maintain a good contact at all times.
_Connections._
Switches for currents of over thirty amperes must be equipped with lugs,
firmly screwed or bolted to the switch, and into which the conducting
wire shall be soldered. For the smaller sized switches simple clamps can
be employed, provided they are heavy enough to stand considerable hard
usage.
Where lugs are not provided, a rugged double-V groove clamp is advised.
A set screw gives a contact at only one point, is more likely to become
loosened, and is almost sure to cut into the wire. For the smaller
sizes, a screw and washer connection with up-turned lugs on the switch
terminal gives a satisfactory contact.
_Spacings._
See “Panel Boards”.
_Switchboards._--The stage switchboard is usually located on the
right-hand side of the stage. This position enables the operator to
watch cues easily and handle his switches with the right hand. This side
is also the one from which the stage manager prefers to work. It is
preferable to have the board raised high enough above stage level to
allow all space on the stage to be used by actors. If the switchboard is
located on stage level it takes up much room that is valuable and makes
stage exits for actors difficult.
The wiring of a good switchboard should be divided into three parts,
each part independent of the others, so that any one part can be
entirely cut off without interfering with the other. All of the house
lights should be fed through one main switch, and all of the stage light
connected to another set of bus-bars, but it is best not to have the
stage side of the board as a whole controlled by a main switch. If the
stage side of the board is controlled by a single switch there exists
the possibility that this switch may be used to cut off everything for a
dark scene and when light is again wanted a part of the lighting of the
previous setting may be left on and possibly interfere with the new
scene.
[Illustration: FIGURE 178.]
The stage lighting is usually divided into four groups, viz.: three
color groups and a group of stage pockets. The number of white lights
is usually equal to that of all of the colors.
Figure 178 shows a well laid out switchboard. All of the lights in the
auditorium are controlled by switches shown in the upper right-hand
corner and all of these are under the control of the main switch. The
house lights are usually thrown on or off as a whole and this main
switch must be convenient for the operator.
The stage pockets are controlled by the bank of switches shown at _E_.
Lights burning off the stage pockets generally are controlled by special
operators on the stage or by actors, and need not be so very convenient
to the switchboard operator. They must, however, be under his control
when necessary; but here also a main switch is not advisable.
In addition to the three groups of lights spoken of above, there are a
number of lights which should be controlled from the switchboard but
must be so connected that they will be left on, no matter what is done
with either house or stage light.
In this group belong a few lights mounted at the top of the switchboard
which enable the operator to see his switches when all else is dark.
These lights are generally shielded so as to throw no light in the
direction of the stage opening. The orchestra lights also belong in this
group, but a special switch may, with advantage, be arranged on this
circuit to bring it under the control of one of the musicians. In some
dark scenes these lights are turned out for a short time, but it is very
important that they be turned on again at the proper moment, and this is
more certainly assured, by giving the musicians control, than by
leaving it to an electrician on the stage who may be very busy with
other matters at the time.
The lights on the fly floor and in the rigging loft, as well as those in
dressing rooms and basement, must also be independent. Fan motor
circuits should also be independent of the house circuit. They are often
needed when the house lights are thrown off.
With the switchboard illustrated in Figure 178 we have shown only the
switches governing the house and stage proper. The switches governing
the other lights are usually worked into the vacant spaces between the
two groups. Each switch should be labeled in such a manner that a new
operator can learn the board easily.
The most important part of the board is that part governing the stage
lighting, and this should always be placed as conveniently as possible
to the operator. A stage switchboard is like a house in that no one is
wholly satisfied with the one he has, but thinks he could improve it a
little if he could build it over again. The arrangement shown in Figure
178 is, however, quite satisfactory for general purposes. The white
lights predominate in the ratio of two to one and are laid out in two
groups _A_ and _B_. Both groups are controlled by the switch _C_. The
switches _A_ and _B_ do not control the lights at all if the smaller
throw-over switches at the right are thrown downward. A diagram of these
switch connections is given in Figure 179 where the switches _B_ and _C_
are indicated. The object of the switches _A_ and _B_ is to help in
quickly increasing or decreasing the illumination on the stage. If in
the beginning of a certain scene, for instance, only a small quantity of
light is wanted, while a little later full illumination is desired, the
low illumination may be obtained by throwing the proper switches down;
the additional illumination which will be needed a few minutes later may
be prepared for by setting the other switches needed to the upward
position and at the proper moment closing switch _B_; this will
instantly produce the effect which otherwise would be possible only by
operating a number of switches in succession. In the same way, by a
reversal of this process, the illumination may be reduced in any amount.
This feature is very valuable in many stage settings.
[Illustration: FIGURE 179.]
To throw off all of the white lights the switch _C_ must be opened. The
switches _D_ and _F_ are main switches controlling colored lamps. All
lamps of one color should be connected to one or the other of these
groups unless some special color effect is desired.
From the three groups of switches, circuits extend into the foot lights,
into every border, and into the proscenium side-light strips so that the
color scheme may be carried out in any of these.
The handles of all switches in a row should be of the same height so
that the operator may more readily accustom himself to catch them
quickly. It is better to have switches of some excess capacity, as the
heavy metal stands the arcing much better.
A main switch by which the whole board may be cut off should be
installed but this need not be on the front of the board.